Field
The present disclosure relates generally to a display module and a method for coating the same using a coating jig device, and for example, to a display module having a coating layer formed thereon to block sidelight of a plurality of luminous elements that are arranged on a printed circuit board, and a method for coating the display module using a coating jig device that guides edges of the printed circuit board the coating layer to surround side portions of the respective luminous elements.
Description of Related Art
In general, an LED display includes a plurality of LED elements mounted thereon at predetermined intervals. Such an LED display is the next generation display system that substitutes for a typical liquid crystal type display, and has the advantages of high color representation and high luminance picture quality. An LED display having specific resolution is composed of unit modules (hereinafter referred to as “display modules”), and several display modules are connectedly attached in the form of a matrix to form a single display.
However, due to a machining error of the sizes of printed circuit boards of respective display modules and a difference in the degree of close contact between the respective display modules that occurs when the respective display modules are installed on a frame in the form of a series array, a mechanical gap may occur between the display modules to cause a black seam to be visually recognized. Accordingly, in the case of connecting the display modules in the related art in the form of a matrix, it is required to put a great deal of effort in order to prevent the machining error from occurring, and it costs a lot in managing the machining error of the printed circuit board.
In addition, a plurality of LED elements mounted on a display module are disposed with the same intervals. When making a multi-vision by connecting the plurality of display modules, there may be a problem of white seam that luminance between display modules is brighter than luminance between LED elements mounted on a single display module. The reason why white seam occurs is as shown below. When making a printed circuit board of a display module, if a margin (a distance from the outermost LED element to an edge of the printed circuit board) of the printed circuit board is formed to be shorter than a predetermined distance, when a printed circuit board having a short margin (hereinafter ‘a first substrate’) is connected to a printed circuit board of another display module (hereinafter ‘a second substrate’), intervals between the LED element arranged at the outermost of the first substrate and the LED element arranged at the outermost of the second substrate are narrower than the intervals among a plurality of LED elements mounted on a single display module. Due to the above, total light quantity between the LED element arranged at the outermost of the first substrate and the LED element arranged at the outermost of the second substrate is larger than total luminance between two columns of a plurality of LED elements mounted on the single display module and accordingly, a phenomenon that a portion between the first substrate and the second substrate that are arranged adjacent to each other looks brighter, i.e., white seam, occurs.
Further, the display module in the related art is provided with an anode electrode and a cathode electrode that are exposed to an outside. These electrodes may cause the LED elements to be burnt when an electrostatic discharge is projected onto the display module. Due to this, there is a high possibility that a control circuit that is electrically connected to the respective electrodes is damaged. In this case, the electrostatic immunity of the LED element becomes 0 to 2 KV and the electrostatic immunity of the control circuit element connected to the LED element becomes about 1 to 4 KV, which do not satisfy the international standard that corresponds to the electrostatic immunity of 8 KV. Accordingly, it is general to cope with overvoltage by designing a TVS (Transient Voltage Suppressor) diode between the cathode electrode and ground. However, in this case, the manufacturing cost of the display module is increased, and the complexity of the circuit design is increased.
As another means for solving the above-described problem, a transparent coating solvent is spread on one surface of the display module, and such a coating process is mainly performed through spraying, potting, and parylene deposition.
However, according to the coating technology in the related art, a transparent coating solvent is attached to an upper surface of the LED element. In the case where the transparent coating layer is formed on the upper surface of the LED element, picture quality may deteriorate and luminous color may be shifted. Accordingly, the transparent coating layer that is formed on the upper surface of the LED element has light refractive index and permeability that are different from those of an LED molding surface, and thus unintended picture quality deterioration and color change may occur. In order to solve this problem, in order to block unintended light that is emitted from four side surfaces of the LED element, a technology to mount and mold the LED element in an opaque package has been proposed. However, such a technology in the related art has the problem that it is very difficult to implement the technology in a display module that uses micro LED elements that are equal to or smaller than 1 mm×1 mm.
Further, Japanese Registered Patent No. 3875768 (published on Feb. 26, 1999) discloses a configuration in which a filler is coated on a display module having a plurality of LED elements. In this case, the display module is provided with a rear cover that simultaneously surrounds the rear surface and the side surface of a printed circuit board so as to prevent the filler that is coated on one surface of the printed circuit board from being spilled. Such display modules are connected to one another in the form of a matrix to be used in a large-sized electronic signboard that is mainly installed outdoors.
Accordingly, such a display module uses LED elements having relatively large size and also has a large pitch between LEDs, and thus there is no difficulty in coating the filler between the respective LEDs.
However, as described above, such a coating technology has the problem that it is unable to be adopted in coating the coating solvent between the micro LED elements having the size of 1 mm×1 mm. Further, since the display module should always be provided with a rear cover, the side surfaces of the respective rear covers of adjacent modules come in contact with each other, and in this case, the black seam may be seen.